About 75% of mail in Belgium is spam, usually associated with shady products or dodgy deals. But spam is just another word for unsolicited publicity mail - an email which you didn't ask for and which is completely useless to you or your business.

If you are sending out emails, be it just one email or in bulk, then consider very carefully if your email is going to be useful to the recipient. The best - and only legal - way is to actually have that recipient ask for the email in the first place - the opt-in. At any time the recipient must be able to revoke his request, and stop receiving further emails - the opt-out.

The law governing this is quite clear, the repercussions of not complying with that law aren't. In Belgium, BIPT - The Belgian Institute of Postal Services and Telecommunications - is concentrating on forcing ISPs - Internet Service Providers - to filter out unsolicited mail. BIPT confirms that they are unable to punish non-compliant ISP's. In any case, it is a useless exercise, as it only protects those companies or individuals who use the ISP's own email service. Those who use external email providers such as Gmail, Live or have their own email server are not benefiting from this.

Companies which send out unsolicited mail are neither targeted nor punished. In practice, the best that Belgium can do is to reprimand non-complying companies.

In the Netherlands, in a landmark case, Opta, the Dutch Independent Post and Telecoms Authority, reprimanded two companies and imposed a total of 510,000 euro fine for sending out unsolicited mail. This seems to be the highest fine ever imposed by Opta for spamming.

"What's the big deal anyway?". A remark we hear very often when discussing personal data issues."Nothing to be concerned about, who would be interested in my personal data, and what can they do with it anyway?"

Everyone agrees that a credit card number or bank account number is not something you should share (even Jeremy Clarkson eventually). But what can people do with my name and address, social security number or date of birth?

Personal data can be used for identity theft - impersonating someone by using as much as you know about that person to get financial or other benefit in that person's name. For example you could go to a bank and request - and receive - a new credit card in the name of the person you are impersonating, with the bills of course being sent to the original person.

How do criminals get their hands on your data? Everybody knows about skimming - a technique where a debit or credit card gets copied by attaching a small device onto an ATM machine. Another well known technique is to steal files from people's computers, by hacking them or by installing viruses or Trojan horses. And of course there is social hacking, asking seemingly harmless questions to a person online or in person, and using that information to build a complete profile.

And criminals move with the times. A BBC team exposed, in a proof of concept, how easy it is to socially hack Facebook and harvest information on other users, including names, passwords and other information.

How do criminals use this data? It seems that data thieves set up data supermarkets to sell stolen personal data to whomever might be interested. Yes, you can get a working credit card number for a few euro, or even buy complete corporate log files (containing names and passwords, server locations, numbers and confidential information) for as little as 200 euro. When closed down, they just reopen on another location.

Stuff to think about. Perhaps you will consider this the next time before revealing some of your personal data to anyone.